So the v-dub has been making knocking noises and has a ton of blow-by. It also went from 495 psi to 450 on 1&4 and 350 on 2&3. Tore it down and holy crap! First, The cam belt was nearly 1/2 gone. OK for about 25K and then
? About 10K ago I was in a race and red lined it when there was a hell of a bang and it knocked like it was going to throw a rod at any moment. It still ran and I was 15 miles from home so I kept on driving. 10 miles later it quieted down so I kept going. It kept the knock but it ran, so I kept driving it. I thought that I had ran it backward and bent a piston skirt but not so. What I found was big indentations from the exh valves in the piston tops. I read some of the posts of people contemplating a hi-po cam and there is no room for error. My timing was an infinitesimal degree off and I think that's what did it. Don't know yet if I've damaged the valves/guides/etc. and that might contribute to the oil consumption/blow-by. What's really weird is the edge of the piston where the jet from the pre-cup comes from is burned away. I've only got 30K on it and at that rate, I could get maybe 100K before it was gone. I plugged the manifold blow-off and the waste gate gives me 15 lbs max. Most of the time it runs around 5-7 psi. The majority of driving is 70 mph on the highway on veg oil. I thought that the veg oil had less BTU's so should burn cooler. Is this a timing issue? (too advanced). There's also some brown deposits on things. Does this happen on regular diesels? Maybe it's hot dog grease impurities. Got some pictures but not doing so well posting them.
ok wow. lol!
The cam belt, possible that you have tightened the tensioner too far and wrecked a bearing somewhere causing the belt to track off and get eaten.
The knock and exh valve indentations.. timing definitely skipped.. however, do you have the Governor Mod done or any pump work? If not and it is just a stock pump you were nowhere near red line
LOL. You were more likely closer to 4300rpms maybbbe a touch higher. Either way myself and a few members with aggressive governor mods have had these engines to 5500+ rpm.
Piston was burned away? You had a leaking injector, dribbling fuel in to the cylinder when not supposed to.. causing SUPER HOT spots. Hot enough to melt Aluminum lol.
I only have BLACK deposits on things, no brown at all.
Yeah, I'm thinking that the tension may have been too tight. Always afraid of the belt jumping time so I probably over compensated. I wonder if the IP bearing might have gone bad. I haven't touched the tension since the initial setting and it might have taken this long for it to wear. Also, there was the hot start issue and maybe I've been sucking air(?). The pump is stock with the only mod being turning the aneroid to max fuel. Red line was just a point of reference. I know they'll do more but I never got to that point and didn't want to without a tach. I've gone through a couple of dozen injectors and nozzles lapping & testing them to get consistant specs. I could see 1 or2 leakers but all of the pistons have the same amount of erosion. I can dump enough fuel to bring darkness to the valley but most of the time it's just cruising. I'm sure that the deposits are from the veg oil though they did seem a bit excessive for a relatively
new engine.
I run on veggie too for longer trips and have moticed that when the wheather is colder the (veg)fuel is restricted in its filter. I run a low pressure fuel pump on the veg and have a pressure/vacuum guage on the fuel before the IP. When it is cold I can get 10 to 15 in of vacuum instead of the normal 2-3 lb. pressure. This retards the timing and at highway speed increases the exhaust gas temps by 2-400 degrees. If it has been cold or your filter is clogged it may have caused the piston melt.
Michiel
MTDI Westy
MTDI syncro Doka
And to add to that if the oil is too cold it won't spray out the injector properly which can cause some interesting yet undesirable things to happen.. What kind of WVO rig do you have??
I think that we might be getting somewhere. First, as for the veg oil. I have learned that there is almost no such thing as too hot. I've got heaters galore and there is virtually no difference in performance when I switch over. That being said, flow is a different matter. I use to change filters every week mostly due to waxing. Things have setteled down after adding more heat. I installed an electric boost pump mainly to over come all the restrictions.
This is my hypothesis as to what's been going on and why things are the way they are now. Way back when I raced it, the crank sprocket jumped a tooth. This retarded the cam & IP. Retarded cam caused the exh valves to hit the pistons making lots of noise. After the valves mashed indentations in the pistons there was less noise. Retarded IP caused late firing and subsequent rise in flame temperature eroding the pistons. This also made it a *** to start when it was hot. Crappy rings on Prothe pistons caused excessive blow-by. Pistons themselves held up well and the crank bearings look fine.
Got new pistons. Will get new rings. Check the valves for being bent or bad guides. Make sure that the belt tracks right and tension is correct.
Get new guides and exhaust valves. They're hammered. Is the engine a solid lifter head? If so, get new exhaust lifters too, you'll see why.
They're hydraulic. Small comfort. I bought a dead head a year ago. The valves are about $34